A USB memory is subject to loss. Several methods are available in the related art to prevent information leak from a lost USB memory. For example, in one method, the USB memory may be locked using a password. In another method, a data file is, encrypted. In yet another method, a data file is deleted in response to a password error.
According to Japanese Unexamined Patent Application Publication No. 2006-338583, there is a storage medium device controlling unauthorized data use for a computer terminal. The storage medium device is detachably loaded onto a computer terminal. The storage medium device includes a storage unit which the computer terminal reads data from and overwrites data on, elapsed time identifying means for identifying time that has elapsed since the storage of data on the storage unit, power source means supplying power at least causing the elapsed time identifying means to be operative, elapsed time judging means judging whether the elapsed time identified by the elapsed time identifying means exceeds a given usable period, and deactivation means deactivating a use of the data stored on the storage unit on condition that the elapsed time identified by the elapsed time identifying means exceeds the given usable period.